It is well known to form a seal between two pipe sections, such as two corrugated pipe sections, where the end of one of the pipe sections has annular grooves and one of the pipe sections has an enlarged bell portion at one end. Some prior art elastomeric gaskets are placed around the end of the pipe section having annular grooves. The pipe section having annular grooves is inserted into an enlarged bell portion of a second pipe section. The elastomeric gasket contacts each of the pipe sections to form a seal between the pipe sections.
Typically, a large frictional force is encountered when the inner pipe and the elastomeric gasket is inserted into the outer pipe. As one end of the inner pipe is pushed into the enlarged end or bell of the outer pipe section or pipe connector, the gasket is sometimes pulled, from the groove by the large frictional force. When the pipe is not properly sealed, ground water may leak into the pipe or fluid may leak out of the pipe and contaminate the ground.
Lubricant has been manually applied to elastomeric gaskets before the inner pipe and the gasket is inserted into the outer pipe. The lubricant reduces the frictional force between the gasket and the outer pipe. The reduced frictional force reduces the likelihood that the gasket will be pulled from the groove by the frictional force. The manual application of the lubricant is labor intensive and is usually performed in a trench or ditch making the lubricant susceptible to being removed by water frequently found in such environments. In addition, the manually applied, lubricant is wiped from the gasket if the pipe joint is disassembled. As a result, the lubricant must be reapplied before the pipe joint is reassembled.
Costly secondary operations have also been developed for applying anti-frictional coatings to gasket surfaces. A secondary operation occurs when the lubricant is applied to the gasket after the gasket is cured. An example applying a lubricant in a secondary operation appears in U.S. Pat. No. 6,328,309 to Corbett. In particular, Corbett depicts a spray-on lubricant that is applied after the gasket is hardened. Secondary operations as taught in Corbett typically require additional steps such as heat treatment and/or prescribed cooling periods before the product is finished. In addition, the spray operations lack the ability to control the thickness of the lubricant coatings and the coatings often crack inhibiting the gaskets ability to stretch or compress without resulting in seal failure.
Prior art methods have been developed that self lubricate gaskets as they are assembled. For example, U.S. Pat. No. 4,365,818 to Tolliver discloses a seal including a cavity containing a lubricant, which is released when one pipe joint is slid over the seal. U.S. Pat. No. 5,143,381 to Temple is directed to a seal, which has an internal chamber containing a lubricant. A slit in the body of the seal extends into the chamber. When one pipe is moved over another pipe end, the slit is spread, thereby releasing the lubricant against the sealing surface. U.S. Pat. No. 5,626,349 to Sutherland et al, concerns a sealing ring containing a lubricant enclosed within a membrane formed on the ring's body. When a connecting pipe is slid into the pipe joint, the membrane is ruptured, releasing the lubricant and reducing the frictional forces imparted on the sealing ring during the joining of the pipes. U.S. Pat. No. 5,735,528 to Olsson discloses a seal containing a lubricant. The lubricant migrates to the surface of the seal, thereby providing self-lubricating properties. Each of these methods provide the lubricant only the first time, or a limited number of times, the gasket forms a seal. The lubricant is eventually wiped off or spent. After the lubricant is wiped off or spent, a lubricant may need to be manually applied to ensure a proper seal.
In Applicant's co-pending application Ser. No. 10/419,541, filed in the U.S. Patent and Trademark Office on Apr. 21, 2003, entitled “PERMANENTLY LUBRICATED GASKET” incorporated herein by reference uses a lubricating agent additive that migrates to the surface of the gasket. This approach lowers the coefficient of friction “COF” and allows the pipe to be assembled without lubrication. The migration results in an oily texture on the surface of the gasket that can be undesirable in certain applications.
Another potential shortcoming of using a migrating lubricating agent or additive is creating a condition having a heightened disposition to contamination. A migrating lubricant agent produces an oily texture on the gasket surface that attracts dust and debris, which can lead to leaks and failure in the pipe joint when assembled. There also exists a problem of chemical migration to areas undesirable of lubrication.
There is a need for a gasket combined with a permanent lubricating chemical film resistant to contamination and propitious to welding operations while maintaining lubrication regardless of the frequency that the joint is assembled and disassembled. In addition there exists a need for a gasket to include a lubricating portion that is integrated within the gasket during the extrusion process eliminating a need for labor and cost intensive secondary operations. While yet a need exists for a gasket having a lubricated portion susceptible to compression and expansion without cracking, while retaining lubrication within a controlled location.